Silyltellurides serve as new silicon-based chemoselective reducing agents and reduce quinones to the corresponding bis-silylated hydroquinones. The reaction proceeds under ambient thermal conditions without the need of any additional promoters or catalysts and gives the products in excellent yields. Several control experiments suggest that the reaction is initiated by a single electron transfer from silyltellurides to quinones.
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A new thermal coupling reaction forms silyloxy imidoyl tellurides 2 from silyl tellurides 1, carbonyl compounds, and phenyl isocyanide [Eq. (1)]. A mechanism that involves the generation of the silyl radical from the silyl telluride and subsequent chemoselective coupling with carbonyl compounds and the isocyanide is proposed.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Imidoylation of organotellurium compounds with isonitriles has been investigated in conjunction with the radical-mediated C1 homologation reaction by using CO and isonitriles. Carbon-centered radicals generated photochemically or thermally from organotellurium compounds react with isonitriles in a group-transfer manner to give the corresponding imidoylated products. Organotellurium compounds have been found to serve as effective precursors of a wide variety of stabilized radicals, namely benzyl, alpha-alkoxy, alpha-amino, and acyl radicals, which take part in the imidoylation with high efficiency. The reactions are compatible with various functional groups, and can be carried out in various solvents including environmentally benign water. The reactivity of isonitriles has been compared with that of CO through competition experiments, and the results indicate that isonitriles are superior to CO as radical acceptors in reactions with stabilized radicals. The origin of the differences has been addressed in theoretical studies with density functional theory calculations using the B3LYP hybrid functional. The calculations suggest that both carbonylation and imidoylation proceed with low activation energies, and that there are virtually no differences in the kinetic sense. Instead, it indicates that thermodynamic effects, namely differences in the stability of the acyl and the imidoyl radicals, control the overall course of the reactions.
Durch thermische Kupplung gelingt die Synthese der (Siloxy)imidoyltelluride 2 aus dem Silyltellurid 1, Carbonylverbindungen und Phenylisocyanid [Gl. (1)]. Es wird ein Mechanismus vorgeschlagen, wonach zunächst aus dem Silyltellurid das Silylradikal gebildet wird, das nachfolgend mit der Carbonylverbindung und dem Isocyanid kuppelt.
A radical idea: A diversity-oriented synthesis of α-amino acid derivatives is realized by the silyltelluride-mediated radical coupling of imines and isonitriles followed by various transformations of the carbon–tellurium bond of the coupling products (see scheme). The α-amino radical generated from the imine and the silyltelluride is the key intermediate in the coupling reaction. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2003/z50184_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
